1. Field of the Invention
This invention relates to a manually actuated fluid flow control valve assembly which is particularly adapted to be used on a railway tak car as a bottom operable lading valve and which has manually releasable means including automatic lock means for holding the valve and an associated manually operated actuating handle for the valve assembly in a closed position.
2. Description of Prior Art
It is well known in the art to provide a valve assembly which is particularly adapted for use on a railway tank car and which is operable from the bottom of such tank car.
It is also known to provide bottom operable butterfly valves for railway tank cars and examples of such butterfly valves are disclosed in U.S. Pat. Nos. 4,016,907 and 4,394,002.
It is also known to provide a manually actuated fluid flow control valve assembly which has an associated support structure and with the valve assembly comprising a valve body having a flow passage therethrough, a closure device carried by the valve body for controlling fluid flow through the passage, a manually operated handle operatively connected to the closure device, with the handle being manually movable between an open and a closed position thereof which define a corresponding open and closed position of the closure device and hence the valve assembly, and manually releasable means for holding such handle in its closed position. An example of such a valve and handle are shown in U.S. Pat. No. 4,397,444.
However, the Association of American Ralroads (AAR) and the Department of Transportation (DOT) have railway tank car regulations which require that projections extending in excess of 1 inch below the bottom of the tank of such a car must be protected by a skid, or if such a projection is part of a valve assembly associated with the tank car it must be capable of being sheared away without affecting the integrity of such valve assembly. In instances where a skid is provided this skid must be in the form of a ramp having a longitudinal dimension along the bottom of the tank which is three times the dimension projecting downwardly from such bottom.
In providing a valve assembly for a tank car, such as a railway tank car, it is important to provide a valve assembly which will not tend to open during normal usage thereof. Further, to assure that each valve assembly will not tend to open, locking means is provided to lock the valve assembly in its closed position to prevent inadvertent opening thereof at any time and in particular to prevent such opening in the event of an accident involving the valve assembly.
Nevertheless, valve assemblies proposed heretofore are deficient because they either do not employ means which provide a positive locking action or such valve assemblies and their associated locking devices and actuating handles are too complex and expensive.